2016-12-20 16:24+0100, Radim Krčmář:
> 2016-12-19 19:15-0800, Kyle Huey:
> > On Mon, Dec 19, 2016 at 12:48 PM, David Matlack <dmatlack@xxxxxxxxxx> wrote:
> >> kvm_skip_emulated_instruction() should not be called after emulating
> >> a VM-entry failure during or after loading guest state
> >> (nested_vmx_entry_failure()). Otherwise the L1 hypervisor is resumed
> >> some number of bytes past vmcs->host_rip.
> >
> > Ah, I see. Sorry for that regression.
> >
> > These paths are supposed to trigger TF-induced singlestep exceptions
> > though. Quoting from the Intel SDM (Vol 3, Chapter 26)
> >
> > "EFLAGS.TF = 1 causes a VM-entry instruction to generate a single-step
> > debug exception only if failure of one of the checks in Section 26.1
> > and Section 26.2 causes control to pass to the following instruction.
> > A VM-entry does not generate a single-step debug exception in any of
> > the following cases: (1) the instruction generates a fault; (2)
> > failure of one of the checks in Section 26.3 or in loading MSRs causes
> > processor state to be loaded from the hoststate area of the VMCS; or
> > (3) the instruction passes all checks in Section 26.1, Section 26.2,
> > and Section 26.3 and there is no failure in loading MSRs"
>
> Changed cases are in section 26.3 => not generating #DB is correct,
>
> Reviewed-by: Radim Krčmář <rkrcmar@xxxxxxxxxx>
>
> Sorry for missing that while applying, I wonder if there is a reason why
> we didn't check them after enter_guest_mode() ...
>
> >> @@ -10517,7 +10517,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
> >> ia32e != !!(vmcs12->host_ia32_efer & EFER_LME)) {
> >> nested_vmx_entry_failure(vcpu, vmcs12,
> >> EXIT_REASON_INVALID_STATE, ENTRY_FAIL_DEFAULT);
> >> - goto out;
> >> + return 1;
My attention is in shambles these days ... this one looks like it is in
section 26.2.2 and should therefore be
nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_HOST_STATE_FIELD);
goto out;
Not a problem of this patch though, I'll go for a minor refactoring
after a beer.
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